<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            width: 300px;
            height: 100px;
            border: 1px solid black;
        }
        #div5{
            width: 100px;
            height: 50px;
            border: 1px solid red;

            margin: 10px;
            /* div5相当于div1是外边距 */
        }
        #div1{
            /* margin: 10px; */
            /* margin 边距，表示外边距 */

            margin-bottom: 10px;

            /* padding: 10px; */
            /* 内边距 
            div1相对于div5是外边距*/
        }
    </style>
</head>
<body>
    <div id="div1">
        <div id="div5">第一个div</div>
    </div>
    <div id="div2">第二个div</div>
    <div id="div3">第三个div</div>
    <div id="div4">第四个div</div>
</body>
</html>